The present invention relates to computer networks, and more specifically to a computer network that provides automatic protection switching to reroute data packets in the event of a network link failure.
In an Internet Protocol (IP) based computer network, data routing protocols such as Open Shortest Path First (OSPF), Intermediate System-Intermediate System (IS-IS), and Routing Information Protocol (RIP) are used to determine the path that data packets travel through the network. When a link between two network routers fails, the routing protocols are used to advertise the failure throughout the network. Most routers can detect a local link failure relatively quickly, but it takes the network as a whole a much longer time to converge. This convergence time is typically on the order of 10-60 seconds depending on the routing protocol and the size of the network. Eventually, all of the involved routers learn of the link failure and compute new routes for data packets to affected destinations. Once all the routers converge on a new set of routes, data packet forwarding proceeds normally.
While the network is converging after a link fails, transient loops can occur which consume valuable bandwidth. Loop prevention algorithms have been proposed to eliminate such transient loops. When using these algorithms, routes are pinned until the network has converged and the new routes have been proven to be loop-free. Loop prevention algorithms have the advantage that data packets flowing on unaffected routes are not disrupted while transient loops are eliminated. The main drawback of loop prevention algorithms is that data packets directed out of a failed link get lost, or xe2x80x9cblack holed,xe2x80x9d during the convergence. Loop prevention algorithms also extend the convergence time somewhat while new routes are being verified to be loop-free.
A preferred embodiment of the present invention includes an apparatus and method for processing data packets in the event of a link failure of a routing node that delivers data packets to a data network via a plurality of links. A protection cycle manager includes a protection cycle packet identifier and a protection cycle packet processor. The packet identifier identifies, as protection cycle packets, data packets having a specific protection cycle format that includes a packet source and a packet destination. The processor processes each protection cycle packet to determine whether the packet destination corresponds to the routing node, and if the packet destination corresponds to the routing node, the protection cycle packet is treated by the routing node as a data packet received from the packet source via the failed link. Otherwise, if the packet destination does not correspond to the routing node, the protection cycle packet is sent to a protection cycle node for the routing node.
A further embodiment may include a protection cycle packeter, that, in response to failure of a link for the routing node, converts affected data packets routed over the failed link into protection cycle packets in the specific protection cycle format. The protection cycle manager may further advertise a link failure to the network using a routing protocol. The specific protection cycle format may include a label stack based on Multi-Protocol Label Switching (MPLS) which may include labels for the packet source and the packet destination. The protection cycle node may be a next node on a Label Switched Path (LSP), in which case, the LSP may be based on network topology information which may be derived from a network protocol.
A preferred embodiment also includes a data router that delivers data packets to a data network via a plurality of links, the router processing data packets in the event of a link failure. The router includes a data interface for data packets to enter and exit the router, and a protection cycle manager. The protection cycle manager includes a protection cycle packet identifier and a protection cycle processor. The packet identifier identifies, as protection cycle packets, data packets having a specific protection cycle format that includes a packet source and a packet destination. The processor processes protection cycle packets to determine whether the packet destination corresponds to the routing node, and: (i) if the packet destination corresponds to the router, the protection cycle packet is treated by the router as a data packet received from the packet source via the failed link, and, (ii) if the packet destination does not correspond to the routing node, the protection cycle packets are sent to a protection cycle node for the router.
Another preferred embodiment includes a computer network having a plurality of data packet streams. The network includes a plurality of subnetworks, each subnetwork having at least one application that generates a stream of data packets for transmission over the computer network, and a plurality of routers that deliver data packets to the network via a plurality of links. At least one router processes data packets in the event of a link failure. The at least one router includes a plurality of data interfaces for streams of data packets to enter and exit the at least one router, and a protection cycle manager having a protection cycle packet identifier and a protection cycle processor. The packet identifier identifies, as protection cycle packets, data packets having a specific protection cycle format that includes a packet source and a packet destination. The processor processes protection cycle packets to determine whether the packet destination corresponds to the routing node, and: (i) if the packet destination corresponds to the at least one router, the protection cycle packet is treated by the at least one router as a data packet received from the packet source via the failed link, and, (ii) if the packet destination does not correspond to the routing node, the protection cycle packets are sent to a protection cycle node for the at least one router.
A preferred embodiment includes a computer program product for use on a computer system for processing data packets in the event of a link failure of a routing node that delivers data packets to a data network via a plurality of links. The computer program product comprises a computer-usable medium having computer-readable program code thereon. The computer readable program code includes program code for identifying, as protection cycle packets, data packets having a specific protection cycle format that includes a packet source and a packet destination. There is also program code for processing protection cycle packets to determine whether the packet destination corresponds to the routing node, and: (i) if the packet destination corresponds to the routing node, the protection cycle packet is treated by the routing node as a data packet received from the packet source via the failed link, and, (ii) if the packet destination does not correspond to the routing node, the protection cycle packets are sent to a protection cycle node for the routing node.